Wet chemical synthesis of S doped Co3O4 nanosheets/reduced graphene oxide and their application in dye sensitized solar cells

Despite the fact that Co3O4 nanomaterials have gained much attention due to their excellent electrochemical properties, the poor conductivity and catalytic reduction ability for I-3 ion hinder their application as counter electrode (CE) of dye sensitized solar cells (DSSCs). Herein, a facile ion exchange approach is developed to prepare S-doped Co3O4 nanosheet. S doping strategy significantly improves the catalytic activity of Co3O4 nanosheets for the reduction of I-3 ion and their charge transport ability. For the sake of doping S into Co3O4 and rGO simultaneously, the similar wet chemical process is adopted in the presence of graphene oxide (GO) to synthesize S-doped Co3O4/reduced graphene oxide (rGO) composites. The power conversion efficiency (PCE) of Co3O4-DSSC is only 1.98%. Using S-doped Co3O4 as CE, the PCE can be dramatically improved to 6.76%. Moreover, the S-doped Co3O4/rGO-DSSC shows higher PCE (8.24%) than that of Pt (7.79%). Electrochemical measurement results indicate that the S-doped Co3O4/rGO composites not only show excellent electrocatalytic activity, but also show high cycling stability. The outstanding improved performance of DSSCs with S-doped Co3O4 nanosheet and S-doped Co3O4/rGO composite as CEs demonstrates that the surface atomic configurations of CE materials have significant influence on their electrocatalytic activity. (C) 2018 Elsevier B. V. All rights reserved.